make physics plugin robust when blocks plugin disabled

lib/plugins/physics.js

@@ -16,7 +16,10 @@ const PHYSICS_TIMESTEP = PHYSICS_INTERVAL_MS / 1000 // 0.05
 
 function inject (bot, { physicsEnabled, maxCatchupTicks }) {
   const PHYSICS_CATCHUP_TICKS = maxCatchupTicks ?? 4
-  const world = { getBlock: (pos) => { return bot.blockAt(pos, false) } }
+  // In setups where the 'blocks' plugin is intentionally disabled to reduce CPU,
+  // bot.blockAt may be undefined. Guard it so the physics plugin can still operate in
+  // packet-scheduling mode (with physicsEnabled=false) without crashing.
+  const world = { getBlock: (pos) => { return (typeof bot.blockAt === 'function') ? bot.blockAt(pos, false) : null } }
   const physics = Physics(bot.registry, world)
 
   const positionUpdateSentEveryTick = bot.supportFeature('positionUpdateSentEveryTick')
@@ -76,7 +79,12 @@ function inject (bot, { physicsEnabled, maxCatchupTicks }) {
   }
 
   function tickPhysics (now) {
-    if (bot.blockAt(bot.entity.position) == null) return // check if chunk is unloaded
+    // If the world plugin is disabled, bot.blockAt may not exist. Only perform the
+    // chunk-loaded check when available. Otherwise, proceed so the plugin can continue
+    // to send movement/keepalive packets without full world state.
+    if (typeof bot.blockAt === 'function') {
+      if (bot.blockAt(bot.entity.position) == null) return // check if chunk is unloaded
+    }
     if (bot.physicsEnabled && shouldUsePhysics) {
       physics.simulatePlayer(new PlayerState(bot, controlState), world).apply(bot)
       bot.emit('physicsTick')